By Ahmad Tabbouch - Created August 2007, originally posted on PodeCoet.org, featured on HackAday

Best cheapshit torch EVER!

Here we have an AWESOME spider-fire CREE LED torch that's begging to be hacked.

It runs on TWO CR123A batteries and is freakin' expensive to maintain (here in Australia CR123's are about $9 each!) - Rather than simply buying a rechargeable set of batteries and a charger to suit, today we'll make it more portable by performing the following modifications:

Force it to run on ONE LiIon CR123A battery by building and installing a boost-converter circuit

Make it rechargeable via a "normal" 5volt external supply, by building and installing an LiIon charger circuit

Install a bicolour LED (or two standard LEDs) to let us know when charging has completed

Warnings / Disclaimers before we get started

The torch will no longer be water resistant

Charging and using the torch simultaneously will create a paradox

Reversing the polarity of a tantCap will cause a fire

Reversing the polarity of the DC input will cause a bigger fire

Reversing the polarity of the battery will set fire to everything kill your dog

No responsibility/liability is accepted for anything. A-N-Y-T-H-I-N-G!

Seriously. If you fuck up somewhere, you WILL set fire to something (I guess it's a win/win!) - Let us begin

Step 1 - Dismantling

First we'll dismantle the torch into its key components. Unscrew the lens assembly and the lower spring / two way switch combo (no need to further dis-assemble these components)

The torch, now in its key components

Step 2 - The modification begins

Now you'll need to drill two holes; one for the DC JACK (using an 8.5mm drillbit) and one for a 5mm LED (using a 5mm drillbit) - If you happen to have a 3mm tricolour LED on hand, or prefer to have seperate RED and GREEN LEDs, modify the aforementioned step to suit your needs. The recommended drilling locations are overlaid on the image below.

Recommended drilling locations

Holes drilled out (not perfect, but shit.)

Step 3 - Prepare the DC socket, LED and your anus

I honestly have no idea where I bought this 1.6mm jack from, but you can easily adapt the modification to whatever you have in your junk box - Simply solder and heatshrink some hookup-wire onto the LED and DC Jack. Leave the wires long, as we'll trim them to size later on

1.6MM DC jack (panel mount) and a COMMON ANODE TriColor LED

...Or make your own common anode TriColour LED ;D

Testfit your DC jack and LED into the empty torch casing. The holes are only SLIGHTLY larger than the actual components, so it might be wise to use some needle-nose pliers when coaxing them into place, as you may have to introduce quite a bit of pressure (tweezers WON'T work, you'll just bend them!)

The LED and DC jack fit snuggly (hooray no glue!)

Step 4 - Prepare the CREE module

You'll need to remove the Anode spring from the CREE LED module then solder a wire in it's place. Simply heat the bottom of the spring with a soldering iron, and gently lift it off

The CREE module with the Anode spring still attached

The CREE module with the Anode spring now removed

The CREE module with a wire soldered in place

Always testfit!

Step 5 - Build and Assemble the PCBs

Etch and Assemble the Boost Converter and LiIon Charger PCBs :: Only the assembled LiIon board is shown below, but you should probably build both. I kept them as seperate PCBs in case you'd like to use either design in other projects (plus it's easier to squeeze two little boards into place, than one larger board)

Un-etched PCB artwork of both the Boost Converter and LiIon charger

Etched LiIon charger PCB

Assembled LiIon charger PCB

Step 6 - Install the Boost Converter

Now we'll set up and install the DC-DC boost converter, this'll step up our 3v7 battery to the 5v required to fully illuminate the CREE module.

As I mentioned before, the torch itself used to run on TWO 3v Lithium batteries. However after some testing, I found that alot of energy was wasted as the LED itself only requires 5 volts. The difference in current consumption between using two batteries and the boost converter circuit is 120mA.

After several trials using both supply types, I found (in practice), using the boost converter as opposed to a second battery only results in a 6-minute loss in the torch's usable time (58 minutes on average with two 3v batteries, 52 minutes on average using a boost converter with ONE 3v7 battery)

CREE module attached to the boost converter circuit

It works! Input: 3v7 @ 1100mA, Output: 5v0 @ 980mA

Now we heatshrink the PCB for protection

...Then shove it in the "free" space indicated by the arrow

Test fit again, to make sure everything sits snuggly

And finally test the build thus far - Hooray no fire!

Step 7 - It all starts coming together

It's time to bring our entire circuit together. We'll start by soldering two wires to the LiIon battery (a little tricky at first), then follow through and cram everything into the case ever-so-gently.

Soldered LiIon Battery

Our layout so far, and wiring guide

Wired up and ready for our cram session!

Whoa, it fit easier than expected! Be sure to Insulate the positive terminal of the battery

Hooray it still works!

Step 8 - Testing the charge circuit

We know it works as a normal torch, but will it charge, or did we damage something during the installation? (I also fucked up, the triColour LED I used was common cathode, so I hacked it up and homebrewed a common anode version using an SMD LED and the remains of the 5mm tricolour LED)

Hooray! Red LED means charging is in progress. Currently drawing 400mA from the PSU

Still charging (drawing 180mA). Added a drop of Epoxy to the LED to act as a lens

*** Update ***

Also modded my kid brother's "SolarForce" torchFLASHLIGHT this morning. Looks almost identical to my SpiderFire torch, so they're probably both knock-offs of another brand

Now I'm out of parts and toner :(

EDIT: It's been brought to my attention that the boost-converter circuit is operating in over-unity, that'd explain the fire in the images above! There may be a few reasonable explanations for this. My method of calculating the current consumption is flawed (simply measuring in series using a DMM, on both the input and the output), the samples for input and output current were taken too far apart (the CREE module draws less as it warms up), or, God did it.

I have no intention of misleading anyone; if anything here seems highly improbable, then it probably is.